The Democratic National Committee plans to announce Wednesday night that it has canceled the final presidential debate in its fall series because of a potential writers strike at CBS News, a sponsor of the debate. [snip][snip]....Sen. Hillary Rodham Clinton (D-N.Y.) was the first candidate to say she would not participate if CBS were the target of a strike, which could be seen as crossing a picket line. Other candidates followed suit. "CBS Evening News" anchor Katie Couric was to be the moderator.